1. Field of the Invention
The present invention relates to the field of semiconductor manufacturing techniques and, more particularly, to an apparatus for processing a semiconductor wafer.
2. Prior Art
In a typical semiconductor integrated circuit fabrication process, integrated circuit devices are constructed onto a preformed semiconductor wafer. These wafers are typically flat and circular in shape. For silicon semiconductor wafers, the diameter of the current wafers vary from approximately four inches to eight inches. By utilizing a number of various processing techniques, which may include doping, implanting, depositing, etching, to name a few, a number of completed integrated circuit "chips" are formed on a given wafer. Subsequently, the wafer is cut to separate each independent chip and then packaged for use.
Due to the trend towards the use of larger diameter wafers and the continued transition toward submicron-dimensioned features, the semiconductor industry is moving toward a single wafer processing technique, instead of the batch processing technique well-known in the prior art for processing smaller diameter wafers. In a typical single wafer processing technique for depositing and/or etching various wafer layers, a single wafer is typically disposed onto a wafer platen ("chuck"), which is typically resident in an enclosed reactor chamber. In order to perform the various depositing and/or etching steps in the manufacture of integrated circuits, various gases are introduced into the reactor chamber under preselected chamber environment to deposit or etch a given layer on the wafer.
With the advent of submicron-dimensioned features, it has become critical to control the tolerances of the various processes in order to control the minute dimensions required of various devices and interconnecting lines in or on the wafer. The construction of the particular reactor chamber, as well as the various processing parameters, such as chamber pressure, gas flow, gas mixture, etc., play a critical role in providing for the submicron-dimensioned features. Thus, many of the prior art reactors are incapable of providing for such tolerances to fabricate submicron-dimensioned integrated circuit devices.
One type of a specialized reactor is a rotating disk reactor (RDR). A RDR includes a reactor chamber with a wafer platen or chuck resident therein. However, unlike other reactors, the wafer chuck of the RDR rotates at a high rate of speed. The rotation of the chuck and the wafer provides for a uniform gas or plasma flow over the wafer which resides atop the chuck. The RDR is exceptionally useful when a thin layer is to be deposited onto the wafer. RDR technology is well-known in the prior art and one such RDR is manufactured and sold by EMCORE Corporation of Somerset, N.J.
One disadvantage of prior art RDRs is the inability of the RDR to switch rapidly from one process gas to another. That is, when one gas mixture is to be replaced by a second gas mixture in the chamber for a subsequent processing step, a finite amount of time is required for the internal environment of the chamber to change completely from the first gas mixture to the second. Unfortunately, reactions continue to occur on the wafer while the gas mixtures are being interchanged and, in many instances, this continued processing is uncontrollable.
Accordingly, it is appreciated that what is desired is a rotating disk reactor which has the capability of subjecting the wafer to rapid switching between the processing gases.